Comparative analysis of potential effects of three phage endolysins against antibiotic-resistant bacteria from the genus Aeromonas

Abstract

Aeromonas species exhibit high antibiotic resistance and—as pathogenic bacteria—are a cause of massive mortality in farmed fish. This emerging increasingly important phenomenon requires new strategies to develop novel antimicrobials. Here, we conducted a comparative study on antimicrobial efficacy of three endolysins (LysPA26, Gp110, and OBPgp279) against antibiotic-resistant bacteria from the genus Aeromonas. Each gene was cloned and expressed with an N-terminal 6×His tag, and the proteins were purified. The purified endolysins manifested antibacterial activities toward Aeromonas species including A. hydrophila, A. salmonicida, and A. veronii without pretreatment with an outer-membrane permeabilizer. The most pronounced effect was exerted by Gp110. The results obtained in vitro were confirmed by in vivo assays because the survival of infected Oreochromis niloticus was better when O. niloticus individuals were treated with endolysin Gp110 in comparison with the other endolysins. Furthermore, effects of intramuscular injection of Gp110 on wound-healing progression were evaluated in Acipenser baerii naturally affected by aeromonosis. The percentage of wound closure in the fish treated with Gp110 was 41.8% on the 6th day, 79% on the 12th day, and 95.7% on the 25th day. Thus, Gp110 is a promising candidate for the development of therapeutics against Aeromonas infections in aquaculture.